The design on the reverse of the note celebrates Scientist, Alan Turing and his pioneering work with computers. It features:
" A mathematical table and formulae from Turing's seminal 1936 paper "On Computable Numbers, with an application to the Entscheidungsproblem" Proceedings of the London Mathematical Society. This paper is widely recognised as being foundational for computer science.
" The Automatic Computing Engine (ACE) Pilot Machine which was developed at the National Physical Laboratory as the trial model of Turing's pioneering ACE design. The ACE was one of the first electronic stored-program digital computers.
" Ticker tape depicting Alan Turing's birth date (23 June 1912) in binary code.
" Technical drawings for the British Bombe, the machine specified by Turing and one of the primary tools used to break Enigma-enciphered messages during WWII.
" The flower-shaped red foil patch on the back of the note is based on the image of a sunflower head linked to Turing's morphogenetic (study of patterns in nature) work in later life.
" A series of background images, depicting technical drawings from The ACE Progress Report.
" Alan Turing's portrait is based on a photo taken in 1951 by Elliott & Fry which is part of the Photographs Collection at the National Portrait Gallery.
" Alan Turing provided the theoretical underpinnings for the modern computer. While best known for his work devising code-breaking machines during WWII, Turing played a pivotal role in the development of early computers first at the National Physical Laboratory and later at the University of Manchester. He set the foundations for work on artificial intelligence by considering the question of whether machines could think. Turing was homosexual and was posthumously pardoned by the Queen having been convicted of gross indecency for his relationship with a man. His legacy continues to have an impact on both science and society today.
"This is only a foretaste of what is to come and only the shadow of what is going to be" is a quote from Alan Turing, given in an interview to The Times newspaper on 11 June 1949. Turing's signature has been taken from the visitor's signature book on display at Bletchley Park Trust in 1947, where he worked during WWII.
Security features: A portrait of the Queen is printed on the window with '£50 Bank of England' printed twice around the edge. A silver foil patch contains a 3D image of the coronation crown above the main see-through window on the front of the note. A metallic, red foil patch contains the letters 'AT' on the back of the note, directly behind the silver crown on the front of the note.
Under ultraviolet light, the number '50' appears in bright red and green on the front of the note. Tactile features of raised print for blind and partially sighted people.
Information is from the Bank of England website and more is available here: http://https://www.bankofengland.co.uk/
Signature: Sarah John. BNYB BE266